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Engineering :: Mass Transfer


91.  In a distillation column the minimum reflux ratio
A. is the maximum ratio which will require an infinite number of trays for the separation desired B. corresponds to the maximum reboiler heat load for the separation desired
C. corresponds to the maximum condenser colling load for the separation desired D. is always zero

92.  For obtaining a given separation in distillation column the minimum number of theoretical stages is obtained with
A. minimum reflux ratio B. optimum reflux ratio
C. total reflux D. zero reflux ratio

93.  Solvent used in extractive distillation
A. alters the relative volatility of the original components B. is of low volatility
C. must form no azeotrope with the original substances D. all of these answers

94.  Entrainer used in azeotropic distillation of binary mixture
A. forms no azeotrope with the original substances B. forms a minimum boiling azeotrope with one or both of the feed components
C. should be of very high viscosity to provide high tray efficiencies D. should have very high latent heat of vaporization

95.  Which of the following is more accurate to determine the number of theoretical stages required for the separation of nonideal binary systems by distillation?
A. McCabe ? Thiele method B. Ponchon ? Savarit method
C. Both McCabe ? Thiele and Ponchon ? Savarit methods are equally good.

96.  McCabe ? Thiele method is used to find the number of theoretical stages required in a distillation operation. This method is based on the assumption(s) that
A. the liquid/vapour loading in each section of the tower remains constant B. Troutons rule is applicable
C. the sensible heat differences are small because the temperature change from tray to tray is small D. all of the above

97.  The flooding in a distillation column is detected by
A. a sharp increase in pressure drop B. a sharp increase in Murphree plate efficiency
C. a sharp decrease in pressure drop D. a sharp decrease in liquid hold up in the column

98.  Entrainment in a distillation column
A. is defined as the liquid carried with the vapour from one tray to the tray above B. is detected by decrease in Murphree plate efficiency
C. may be detrimental since it can carry non-volatile constituents upward D. all of these answers

99.  Inside the distillation column
A. the driving for the vapour flow is the pressure drop B. the driving force for the liquid flow is its weight
C. the liquids and vapours are always at their bubble point and dew point respectively D. all of these answers

100.  Inside the distillation column
A. the pressure decreases gradullay from bottom to top of the column B. the highest temperature is at the top of the column
C. the pressure increases gradually from bottom to top of the column D. the pressure remains constant




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